Process for the purification of
methyl ethyl ketone



United States Patent 3,198,837 PROCESS FGR THE PURIFICATIQN 0F METHYLETHYL KETUNE Jiirgen Smidt, Munich-Sella, Hugo Kojer, Munich, Ru-

dolf Riittinger, Beisenhofen, and Rolf Sieher, Cologne- Longerich,Germany, assignors to Consortium fiir Elehtrochemische lndustrieG.m.b.H., Munich, Germany No Drawing. Filed Dec. 21, 1961, Ser. No.161,261 Claims priority, application Germany, Dec. 24, 1960,

1 Claim. (Cl. 260-593) The present invention relates to a process forthe purification of methyl ethyl ketone which in addition to water andaldehydes also contains chlorination products, especially3-chlorobutanone-2. Such cmorination products, for example, arecontained in methyl ethyl ketone produced by the oxidation of butylenein the presence of platinum metal catalysts containing chlorides in thegas or liquid phase.

It is not possible to remove the impurities indicated in strictlydistillative processes. Also, upon treatment with dilute aqueous alkali,either by boiling under reflux or by extractive distillation, it has notbeen possible toachieve a satisfactory purification. These processes,which have been described with reference to methyl ethyl ketone of otherorigin and composition, are not suitable for the purification of themethyl ethyl ketone concerned according to the invention.

According to the invention it was found that methyl ethyl ketonecontaining water and aldehydes as well as chorination products, such as3-chlorobutanone-2, can be purified by treating the impure methyl ethylketone in intimate contact with 30% by weight aqueous alkali metalhydroxide at temperatures of 90-150 C. under pressure and afterseparation of the layers distilling the methyl ethyl ketone from theorganic phase. Preferably, the methyl ethyl ketone is subjected to asimple prepurification prior to such treatment, such as, for example, bysimple distillation and degasification.

Any alkali metal hydroxide can be employed in the present process. Foreconomic reasons, however, the hydroxides of sodium and potassium arepreferred.

Despite the high temperatures and strong alkali employed according tothe invention, practically no losses of methyl ethyl ketone aresuffered. Such a favorable result was not to be expected in view ofmethyl ethyl ketones own tendency to aldol formation which in thepresence of aqueous NaOH at room temperature already leads to theformation of small quantities of 3-methylheptano1-3-one-5. Prior totreatment with the aqueous alkali metal hydroxide solution it isexpedient to remove the major portion of the 3-chlorobutanone-2 and thewater content above that of azeotropic composition in the crude ketoneby simple distillation. Low boiling compounds, such as acetaldehyde canbe removed in a degasification column.

The actual treatment with the alkali is effected in apparatus whichprovides for intensive mixture of both phases which to a far reachingdegree are insoluble in each other. Vessels with especially eflicientrapidly running stirrers, mechanical high frequency mixers, flow tubes,mixing pumps and mixing nozzles and the like are suited. The periodrequired for the treatment with the alkali, depending upon the type ofmixing apparatus and the temperature employed, can be between about 1and 30 minutes. The volumetric ratio of crude ketone to aqueous alkaiexpediently is selected between 2:1 and 1:20. The mixing apparatus iseither constructed of or clad with such corrosion resistant materials as-CrNiMo steels, Hastelloy, titanium, titanium alloys,

3,198,837 Patented Aug. 3, 1955 "ice ceramics, carbon, graphite,polyolefins, polytetrafluoroethylene or alkali resistant syntheticresins.

The alkali treatment not only converts the aldehyde: contained in thecrude ketones into higher moleculal Weight compounds but also causesdestruction of lihi chloroketones to such a far reaching degree thatthey no longer are a detriment in the further purification. A furtheradvantage of the treatment with the concentrated aqueous alkali is thatthe water content of the crude ketone is reduced considerably thereby.The water still remaining in the crude ketone, about 25%, can easily beremoved by distillation under normal pressure with low steamrequirements. It is possible in this way it avoid costly water removalby distillation under pressure or extractive distillation.

After the alkali treatment the phases are separated All or a part of theseparated aqueous alkali phase car be reused after distilling off thewater and methyl ethy' ketone taken up during the treatment of the crudemethy ethyl ketone. The organic phase is first dehydrated b distillingbit the methyl ethyl ketone-water azeotrope which is recycled to thealkali treatment and then freec' of the higher boiling components in afurther column The lower portion of the latter column is either constructed as a thin film evaporator or as a normal columi in the eventthat a higher boiling auxiliary liquid is em ployed to drive oif themethyl ethyl ketone. The methy ethyl ketone thus obtained meets thecustomary com mercial purity requirements. If special requirement mustbe met, a further more far reaching purification ac cording to knownmethods can be carried out.

The following examples will serve to illustrate sev eral embodiments ofthe process according to the inven tion, all percentages in the examplesare by weight.

Example 1 A pre-purified methyl ethyl ketone which had been pro ducedaccording to the process of German Patent 1,049, 845 and in addition to11.8% water and 1.5% butyralde hyde also contained 0.06% of3-chlorobutanone-2 wa intimately mixed with an equal volume of 25%aqueou NaOH at C. under pressure in a vessel provider with an impellerstirrer. After 25 minutes treatmen the stirring was interrupted and theorganic phase wln'cl separated off over the aqueous alkali layer wasdraw] 01?. The methyl ethyl ketone thus obtained is free 0chlorobutanone and at the same time its water conten had been reduced to4.5% and the butyraldehyde conten to 0.03%. Water was removed from suchproduct b distillation at atmospheric pressure and'the methyl ethyketone-water azeotrope recovered at the head of th column was recycledto the alkali treatment of a furthe batch of methyl ethyl ketone. Theremaining dehydrate methyl ethyl ketone was then distilled in anothercolurrr to separate it from the higher boiling components.

Example 2 A pre-purified crude ketone obtained in the oxidatio ofbutylene in the presence of platinum metal chlorid containing catalystswhich in addition to 11.5% of wate and 0.46% of butyraldehyde contained0.2% of 3-chlc robutanone-2 was treated under pressure at C. wit 20%aqueous NaOH in a homogenizing apparatus. Th volumetric ratio of aqueousNaOH to ketone was 4:1 After 15 minutes treatment the phases werepermitte to separate and the organic phase drawn off. The pro: not wasfree of chlorobutanone. Its water content ha been reduced to 3.7% andits butyraldehyde content t 0.02%. The product was then subjected to thedistill: tion procedure described in Example 1 to separate tb water andthe higher boiling components.

We claim A process for purifying methyl ethyl ketone obtained 1 theoxidation of butylene in the presence of a platinum ietalcatalystcontaining chlorides which in addition to ater and aldehydes containschlorination products as npurities which comprises contacting suchmethyl ethyl etone with a 20 to 30% aqueous alkali metal hydroxide, 1eratio of such methyl ethyl ketone to aqueous alkali letal hydroxidebeing 2:1 to 1:20 by volume, at a temerature of 90 to 150 C. undersuperatmospheric pres- Jre for a period of 1 to 30 minutes, separating01f the rganic phase and recovering purified methyl ethyl ketone om suchorganic phase by distillation.

References Cited by the Examiner UNITED STATES PATENTS 2,429,484 10/47Peters 260-593 X 2,662,848 12/53 Emerson et a1 260-593 X FOREIGN PATENTS817,149 7/59 Great Britain. 878,065 9/61 Great Britain.

LEON ZITVER, Primary Examiner.

